A heavy duty tire fitted to a large vehicle, such as a dump truck, is provided with a plurality of center blocks disposed in a central region of the tread surface in the tire width direction. Such a heavy duty tire can effectively improve in wear resistance and cut resistance in the central region by increasing a contact area of the center blocks. However, an increased contact area of the center blocks increases the block volume and thus lessens heat resistance, causing tire durability to be lessened in some cases.
Conventional heavy duty tires provided with a plurality of center blocks formed on tread surfaces include, for example, a tire according to Japanese Unexamined Patent Application Publication No. H09-136514A. The heavy duty tire according to Japanese Unexamined Patent Application Publication No. H09-136514A includes, in a tread, at least one circumferential groove extending in the circumferential direction and a large number of lateral grooves connecting with the circumferential groove and disposed on both sides of the circumferential groove while being separated from each other in the circumferential direction. In the pneumatic tire:
(1) the circumferential groove extends in the circumferential direction in a tread central region that corresponds to 50% of the tread width;
(2) the depth of the circumferential groove is 5% of the tread width or greater; and
(3) the depth of at least lateral grooves disposed in both side sections of the tread among the lateral grooves is 109% of the depth of the circumferential groove or greater.
According to Japanese Unexamined Patent Application Publication No. H09-136514A, this heavy duty tire achieves good traction performance in traveling on a bad road and wet performance in traveling at high speed in a compatible manner.
Unfortunately, the tire according to Japanese Unexamined Patent Application Publication No. H09-136514A has insufficient heat resistance.
If, for example, a groove extending in the tire circumferential direction is provided in center block regions to enhance heat resistance, it is expected that heat buildup in the center blocks is prevented and that heat resistance is enhanced. However, stones are readily lodged in the groove especially in traveling off-road.